∫x / (x²+a²)^2/3 dx
= 1/2 ∫ 1 / (x²+a²)^2/3 dx² ------ dx² = 2x dx
= 1/2 ∫(x²+a²)^(- 2/3) d(x²+a²) --------d(x²+a²) = dx²
= 3/2 * (x²+a²)^(1/3) + C -------- dx^n = x^(n + 1) / (n + 1)